After purification from extracts of whole cells. Ml RNA, the catalytic subunit of ribonuclease P from Escherichia coli, apparently must undergo a change in conformation before it can function catalytically. The rate of this conformational change is dependent upon the duration of incubation at various temperatures and pH. ΔE* of the transition at pH 7.5 is approximately 36 kcal/mol. The change in conformation is not sensitive to Mg2+ concentration between 10 and 100 mM. A decrease in A260 of Ml RNA in solution has been observed during the incubation period that potentiates the conformational change at 30 °C, but no direct correlation can yet be made to specific structural rearrangements.
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